The invention relates to therapeutic compositions that can be used to prevent and treat infection of human and animal subjects by a pathogen, and specifically to protein-based therapeutic compositions that can be used for the prevention and treatment of viral or bacterial infections. The invention also relates to therapeutic protein-based compositions that can be used to prevent or ameliorate allergic and inflammatory responses. The invention also relates to protein-based compositions for increasing transduction efficiency of a recombinant virus, such as a recombinant virus used for gene therapy.
Influenza is a highly infectious acute respiratory disease that has plagued the human race since ancient times. It is characterized by recurrent annual epidemics and periodic major worldwide pandemics. Because of the high disease-related morbidity and mortality, direct and indirect social economic impacts of influenza are enormous. Yearly epidemics cause approximately 300,000 hospitalizations and 25,000 deaths in the United States alone. Four pandemics occurred in the last century; together they caused tens of millions of deaths. Mathematical models based on earlier pandemic experiences have estimated that 89,000-207,000 deaths, 18-42 million outpatient visits and 20-47 million additional illnesses will occur during the next pandemic (Meltzer, M I, Cox, N J and Fukuda, K. (1999) Emerg Infect Dis 5:659-671).
Influenza is typically caused by infection of two types of viruses, Influenza virus A and Influenza virus B (the third type Influenza virus C only causes minor common cold like symptoms). They belong to the orthomyxoviridae family of RNA viruses. Both type A and type B viruses have 8 segmented negative-strand RNA genomes enclosed in a lipid envelope derived from the host cell. The viral envelope is covered with spikes that are composed of three types of proteins: hemagglutinin (HA) which attaches virus to host cell receptors and mediates fusion of viral and cellular membranes; neuraminidase (NA) which facilitates the release of the new viruses from host cells; and a small number of M2 proteins which serve as ion channels.
Infections by influenza type A and B viruses are typically initiated at the mucosal surface of the upper respiratory tract. Viral replication is primarily limited to the upper respiratory tract but can extend to the lower respiratory tract and cause bronchopneumonia that can be fatal.
Influenza viral protein hemagglutinin (HA) is the major viral envelope protein. It plays an essential role in viral infection. The importance of HA is evidenced by the fact that it is the major target for protective neutralizing antibodies produced by the host immune response (Hayden, F G. (1996) In Antiviral drug resistance (ed. D. D. Richman), pp. 59-77. Chichester, UK: John Wiley & Sons Ltd.). It is now clear that HA has two different functions in viral infection. First, HA is responsible for the attachment of the virus to sialic acid cell receptors. Second, HA mediates viral entry into target cells by triggering fusion of the viral envelope with cellular membranes.
HA is synthesized as a precursor protein, HA0, which is transferred through the Golgi apparatus to the cell surface as a trimeric molecular complex. HA0 is further cleaved to generate the C terminus HA1 (residue 328 of HA0) and the N terminus of HA2. It is generally believed that the cleavage occurs at the cell surface or on released viruses. The cleavage of HA0 into HA1/HA2 is not required for HA binding to sialic acid receptor; however, it is believed to be necessary for viral infectivity (Klenk, H D and Rott, R. (1988) Adv Vir Res. 34:247-281; Kido, H, Niwa, Y, Beppu, Y and Towatari, T. (1996) Advan Enzyme Regul 36:325-347; Skehel, J J and Wiley, D C. (2000) Annu Rev Biochem 69:531-569; Zambon, M. (2001) Rev Med Virol 11:227-241.)
Currently, influenza is controlled by vaccination and anti-viral compounds. Inactivated influenza vaccines are now in worldwide use, especially in high-risk groups. The vaccine viruses are grown in fertile hen's eggs, inactivated by chemical means and purified. The vaccines are usually trivalent, containing representative influenza A viruses (H1N1 and H3N2) and influenza B strains. The vaccine strains need to be regularly updated in order to maintain efficacy; this effort is coordinated by the World Health Organization (WHO). During inter-pandemic periods, it usually takes 8 months before the updated influenza vaccines are ready for the market (Wood, J. (2001) Phil Trans R Soc Lond B 356:1953-1960). However, historically, pandemics spread to most continents within 6 months, and future pandemics are expected to spread even faster with increased international travel (Gust, I D, Hampson, A W., and Lavanchy, D. (2001) Rev Med Virol 11:59-70). Therefore it is inevitable that an effective vaccine will be unavailable or in very short supply during the first waves of future pandemics.
Anti-viral compounds have become the mainstay for treating inter-pandemic diseases. Currently, they are also the only potential alternative for controlling pandemics during the initial period when vaccines are not available. Two classes of antiviral compounds are currently on the market: the M2 inhibitors, such as amantadine and rimantadine; and the NA inhibitors, which include oseltamivir (Tamiflu) and zanamivir (Relenza). Both classes of molecules have proven efficacy in prevention and treatment of influenza. However, side effects and the risk of generating drug-resistant viruses remain the top two concerns for using them widely as chemoprophylaxis (Hayden, F G. (1996) In Antiviral drug resistance (ed. D. D. Richman), pp. 59-77. Chichester, UK: John Wiley & Sons Ltd.). Most importantly, future pandemic strains, either evolved naturally or artificially created by genetic engineering in bio-warfare, may be resistant to all the available anti-viral compounds, and this will have devastating consequences globally.
In summary, currently available vaccination and anti-viral compounds are limited by some fundamental shortcomings. Novel therapeutic and prophylactic modalities are needed to address future influenza pandemics.
Respiratory tract infections (RTIs) are the most common, and potentially most severe, types of infectious diseases. Clinically, RTIs include sinusitis, otitis, laryngitis, bronchitis and pneumonia. Based on numerous etiology and epidemiology studies, it is clear that although many microorganisms have the potential to cause RTIs, only a handful of pathogens are responsible for vast majority of the cases. Such pathogens include S. pneumoniae, M. pneumoniae, H. influenzae, M. catarrhalis, influenza A & B, and parainfluenza virus. Besides causing CAP and AECB, several of the bacterial pathogens, such as S. pneumoniae and H. influenzae, are also the common cause of acute sinusitis, otitis media, as well as invasive infections leading to sepsis, meningitis, etc. Therefore these microorganisms are of the highest clinical importance.
One common feature of all respiratory pathogenic bacteria is that they establish commensal colonization on the mucosal surface of the upper airway; such colonization precedes an infection and is prerequisite for infections. The bacterial colonization in a neonate occurs shortly after birth. During lifetime, the upper airway, specifically the nasopharynx and oropharynx, remains a dynamic ecological reservoir of microbial species with bacteria being acquired, eliminated and re-acquired continually. In most cases the bacterial flora in the pharynx is harmless. However, when the condition of the host is altered, some microorganisms may invade adjacent tissues or bloodstream to cause diseases. In addition to serving as the port of entry for mucosal and invasive infections by both bacteria and viruses, the nasopharynx is also the major source of spreading the pathogenic microorganisms between individuals, as well as the reservoir where antibiotic-resistant bacteria are selected (Garcia-Rodriguez and Martinez, J Antimicrob Chemother, (2002) 50(Suppl S2), 59-73; Soriano and Rodriguez-Cerrato, J Antimicrob Chemother, (2002) 50 Suppl S2, 51-58). It is well established clinically that individuals who are prone to RTIs tend to be persistent and recurrent carriers of the pathogenic bacteria (Garcia-Rodriguez and Martinez, J Antimicrob Chemother, (2002) 50(Suppl S2), 59-73; Mbaki et al., Tohoku J Exp. Med., (1987) 153(2), 111-121).
Helicobacter pylori is a human pathogen implicated in gastritis and peptic ulcer. The bacterium resides in the human stomach and binds to epithelial cells of the gastric antrum. It has been demonstrated that the bacterial adhesion is mediated by binding of Helicobacter pylori adhesin I and II to sialic acids on the epithelial surface.
Siglecs (sialic acid binding Ig-like lectins) are members of the immunoglobulin (Ig) superfamily that bind to sialic acid and are mainly expressed by cells of the hematopoietic system. At least 11 siglecs have been discovered and they seem to exclusively recognize cell surface sialic acid as the ligand. It is believed that the binding of siglecs to sialic acid mediates cell-cell adhesion and interactions (Crocker and Varki, Trends Immunol., (2001) 22(6), 337-342; Angata and Brinkman-Van der Linden, Biochim. Biophys. Acta, (2002) 1572(2-3), 294-316). Siglec-8 (SAF-2) is an adhesion molecule that is highly restricted to the surface of eosinophils, basophils, and mast cells, which are the central effector cells in allergic conditions including allergic rhinitis, asthma and eczema. Siglec-8 is considered to be responsible for mediating the recruitment of the three allergic cell types to the airway, the lungs and other sites of allergy. Siglec-1 (sialoadhesion) and siglec-2 (CD22) are the adhesion molecules on macrophages and B cells, both types of cells play central roles in immune reactions that lead to inflammation.
Recombinant viruses, in particular adeno-associated virus (AAV), can be used to transfer the wild type cystic fibrosis transmembrane conductance regulator (CFTR) gene into the epithelial cells to correct the genetic defect that causes cystic fibrosis (Flotte and Carter, Methods Enzymol., (1998) 292, 717-732). Clinical trials with AAV vectors have shown efficient and safe delivery of the CFTR gene into epithelial cells with low levels of gene transfer (Wagner et al., Lancet, (1998) 351(9117), 1702-1703). Compared to adenoviral vectors, AAV offers more stable gene expression and diminished cellular immunity. However, the transduction efficiency of AAV in vivo is rather low in the lung (Wagner et al., Lancet, (1998) 351(9117), 1702-1703). A method that can improve transduction efficiency of AAV in vivo is needed to achieve full therapeutic potential of gene therapy for cystic fibrosis. It has been shown that negatively charged carbohydrates, such as sialic acid, inhibit the transduction efficiency of AAV vector to the well-differentiated airway epithelium, and treatment of the airway epithelium by glycosidases, including a neuraminidase, and endoglycosidase H, enhances transduction efficiency of the AAV vector (Bals et al., J Virol., (1999) 73(7), 6085-6088).